The present invention relates to an ultraviolet radiation-absorbing, colorless, transparent soda-lime-silica glass, as well as to glass bottles formed out of the glass. In more detail, the present invention relates to an ultraviolet radiation-absorbing, colorless, transparent soda-lime-silica glass as well as to glass bottles formed out of the glass which has no greenish or bluish tint and which can prevent coloration, discoloration, fading in color or deterioration of the flavor of the contents caused by ultraviolet radiation and, inter alia, coloration of refined xe2x80x9csakexe2x80x9d, coloration or fading in color of wines, and deterioration of the flavor of refined xe2x80x9csakexe2x80x9d and wines.
In order to prevent light-induced coloration, discoloration, fading in color or deterioration of the flavor of their content beverages, amber, green or blue bottles have been widely used for refined xe2x80x9csakexe2x80x9d or for beer. All of those glass bottles are deeply colored, which prevent their contents from being seen clearly as they are through the bottles. Thus, there have been needs for transparent, colorless glass bottles with high brightness which thereby allow their contents to be seen more clearly.
In majority of cases, however, transparent, colorless glass with high brightness has, at the same time, high transmittance to ultraviolet radiation. Ultraviolet radiation passing through a glass bottle is apt to induce coloration, discoloration or fading in color of its contents. In the case where its content is refined xe2x80x9csakexe2x80x9d, inter alia, its flavor would be deteriorated along with a yellowing in color, thereby greatly impairing its commodity value. In the case of wines, there also are problems of their coloration or fading in color and deterioration of their flavor.
As a means to solve these problems, an ultraviolet radiation-absorbing, colorless soda-lime glass is disclosed in Japanese Unexamined Patent Publication No. S52-47812. In this patent, the glass contains CeO2 and V2O5 as ultraviolet radiation absorbents, and MnO2 or Se and, as needed, Co3O4 as decolorizing agents. This glass, however, runs a substantial risk of undergoing coloration as a result of solarization because of coexistence of CeO2 and V2O5. Japanese Patent No. 2528579 and Japanese Laid-open Patent Publication No. H8-506314 disclose glasses absorbing ultraviolet and infrared radiation which contains Fe2O3, FeO, CeO2 and manganese oxide. However, as these glasses have a high total iron content together with a high content of FeO, a green to blue color in these glasses is unavoidable. This renders those glasses unsatisfactory as glasses used for producing colorless, transparent bottles with high brightness that allow their contents to be seen more clearly.
Therefore, colorless, transparent, ultraviolet radiation-absorbing glass bottles have been needed which, while allowing their contents to be seen clearly on a store shelf due to their high transmittance to light in the visible region, enable to keep their contents from being exposed to ultraviolet radiation in the process of distribution and on a store shelf.
The objective of the present invention is to provide an ultraviolet radiation-absorbing, colorless, transparent soda-lime-silica glass as well as to glass bottles formed out of the glass which, while maintaining high transmittance to light in the visible region and thereby allowing the contents to be seen clearly, absorbs ultraviolet radiation and thereby prevents coloration, discoloration, fading in color or deterioration of the flavor of the contents caused by ultraviolet radiation.
The present inventors found, as a result of repeated studies to reach the above objective, that an ultraviolet radiation-absorbing, colorless, transparent soda-lime-silica glass is obtained which is highly absorptive of ultraviolet radiation while having high transmittance to visible light, by adding to a conventional basic composition of soda-lime-silica glass specific proportions of SO3, cerium oxide, Fe2O3, FeO, manganese oxide and, as needed, cobalt oxide. The present invention was accomplished based on this finding.
Thus, the present invention provides an ultraviolet radiation-absorbing, colorless, transparent soda-lime-silica glass which is characterized in that its composition includes, in % by weight,
Herein, xe2x80x9ccerium oxidexe2x80x9d means both of CeO2 and Ce2O3, and its xe2x80x9c% by weightxe2x80x9d is expressed as a value obtainable when all the contained cerium oxide is replaced with CeO2. Likewise, xe2x80x9cmanganese oxidexe2x80x9d means both of MnO and Mn2O3, and its xe2x80x9c% by weightxe2x80x9d is expressed as a value obtainable when all the contained manganese oxide is replaced with MnO. In addition, xe2x80x9ccobalt oxidexe2x80x9d is also expressed as a value obtainable when all the contained cobalt oxide is replaced with CoO.
The present invention further provides a glass bottle formed out of the above-identified ultraviolet radiation-absorbing, colorless, transparent soda-lime-silica glass.
As mentioned above, the compositional characteristic of the ultraviolet radiation-absorbing, colorless, transparent soda-lime-silica glass of the present invention consists in that it contains, in specific proportions, SO3, cerium oxide, Fe2O3, FeO, manganese oxide and, as needed, cobalt oxide. The basic composition of soda-lime-silica glass may be in a conventional range. However, considering needs for high chemical durability, eliminated possibility of devitrification and proper easiness of melting, it is preferable that the ultraviolet radiation-absorbing, colorless, transparent soda-lime-silica glass of the present invention typically comprises, in % by weight:
In addition, to enhance the reliability of the total performance of the glass of the present invention, it is more preferable that the ultraviolet radiation-absorbing, colorless, transparent soda-lime-silica glass of the present invention is characterized in that its composition includes, in % by weight,
Furthermore, to further enhance the reliability of the total performance of the glass of the present invention, it is most preferable that the ultraviolet radiation-absorbing, colorless, transparent soda-lime-silica glass of the present invention is characterized in that its composition includes, in % by weight,
Furthermore, it is more preferable that the ultraviolet radiation-absorbing, colorless, transparent soda-lime-silica glass of the present invention comprises, in % by weight:
Still further, it is most preferable that the ultraviolet radiation-absorbing, colorless, transparent soda-lime-silica glass of the present invention comprises, in % by weight:
On a transmittance curve obtained with a 3.5-mm thick sample, the ultraviolet radiation-absorbing, colorless, transparent soda-lime-silica glass of the present invention preferably has transmittance of not more than 4.5 % at the wavelength of 330 nm and, in the visible region of 420-780 nm, transmittance of not less than 88 % without having absorption at any particular wavelength.
In addition, the ultraviolet radiation-absorbing, colorless, transparent soda-lime-silica glass of the present invention preferably has dominant wavelength (xcexd) at 565-575 nm.
The ultraviolet radiation-absorbing, colorless, transparent soda-lime-silica glass of the present invention has an excellent ability to absorb ultraviolet radiation, in particular ultraviolet radiation at the wavelength of 330 nm. Therefore, when used in the form of glass bottles, it can prevent coloration, discoloration, fading in color or deterioration of the flavor of their contents caused by light, and is highly effective, inter alia, in preventing not only a yellowing in color and deterioration of the flavor of refined xe2x80x9csakexe2x80x9d, which is sensitive to ultraviolet radiation at wavelengths around 330 nm, but also coloration, fading in color or deterioration of the flavor of wines.